\begin{tabular}{lrrrr}
\toprule
                          & \multicolumn{3}{c}{SepalLength} & \multicolumn{1}{c}{SepalWidth} \\ 
\cmidrule(lr){2-4} \cmidrule(lr){5-5} 
                          &      (1) &      (2) &       (3) &                            (4) \\ 
\midrule
(Intercept)               & 6.526*** &          &           &                                \\ 
                          &  (0.479) &          &           &                                \\ 
SepalWidth                &   -0.223 & 0.432*** &  0.506*** &                                \\ 
                          &  (0.155) &  (0.081) &   (0.103) &                                \\ 
PetalLength               &          & 0.776*** &  0.830*** &                        1.048** \\ 
                          &          &  (0.064) &   (0.069) &                        (0.362) \\ 
PetalWidth                &          &          &   -0.312* &                                \\ 
                          &          &          &   (0.154) &                                \\ 
SepalLength               &          &          &           &                         -0.313 \\ 
                          &          &          &           &                        (0.239) \\ 
\midrule
SpeciesDummy              &          &      Yes &       Yes &                            Yes \\ 
isSmall                   &          &          &       Yes &                                \\ 
\midrule
Estimator                 &      OLS &      OLS &       OLS &                             IV \\ 
\midrule
$N$                       &      150 &      150 &       150 &                            150 \\ 
$R^2$                     &    0.014 &    0.863 &     0.867 &                          0.080 \\ 
Adjusted $R^2$            &    0.007 &    0.860 &     0.861 &                          0.055 \\ 
Within-$R^2$              &          &    0.642 &     0.595 &                         -0.535 \\ 
$F$                       &    2.074 &   32.900 &    26.861 &                         21.199 \\ 
$F$-test $p$ value        &    0.000 &    0.000 &     0.000 &                          0.000 \\ 
First-stage $F$ statistic &          &          &           &                         19.962 \\ 
First-stage $p$ value     &          &          &           &                          0.000 \\ 
Degrees of Freedom        &      148 &      145 &       142 &                            145 \\ 
\bottomrule
\end{tabular}
